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<h1>Silicon dioxide, SiO<sub>2</sub></h1>

Silicon dioxide (SiO<sub>2</sub>), commonly known as silica, is found naturally in several crystalline forms, the most notable being quartz. Additionally, when silicon dioxide is manufactured without the crystalline structure, it forms what is known as fused silica. Fused silica is a non-crystalline (or amorphous) form of silicon dioxide and is produced by melting high purity silica at extremely high temperatures. It has superior optical clarity, especially in the ultraviolet (UV) range, and is resistant to thermal shock, making it valuable for many high-end optical applications, including lenses and windows in spacecraft and satellites. SiO<sub>2</sub> is extensively used in electronics as an insulator and serves as a primary ingredient in the production of glass. It's also used in thin-film optics, often as antireflection coatings on optical devices. Beyond its optical applications, silicon dioxide finds use in ceramics, construction, and even as a food additive.

<h2>Other names</h2>
<ul>
<li>Quartz</li>
<li>Silica</li>
<li>Silicon oxide</li>
<li>Silicon(IV) dioxide</li>
</ul>

<h2>Polymorphs</h2>
<ul>
<li>Alpha quartz (α-quartz, most common)</li>
<li>Beta quartz (β-quartz, only stable at temperatures above 573 °C)</li>
<li>Tridymite</li>
<li>Cristobalite</li>
<li>Coesite</li>
<li>Stishovite</li>
<li>Lechatelierite</li>
<li>Chalcedony</li>
</ul>

<h2>External links</h2>
<ul>
<li><a href="https://en.wikipedia.org/wiki/Silicon_dioxide">Silicon dioxide - Wikipedia</a></li>
<li><a href="https://en.wikipedia.org/wiki/Fused_quartz">Fused quartz - Wikipedia</a></li>
<li><a href="https://www.webelements.com/compounds/silicon/silicon_dioxide.html">Silicon dioxide - WebElements</a></li>
<li><a href="http://www.minerals.net/mineral/quartz.aspx">Quartz - The Mineral and Gemstone Kingdom</a></li>
</ul>
